Dynamic positioning (DP) is a computer control system to maintain a position of a vessel against environmental forces of current, wind and/or waves. The control system maintains position using propellers and/or thrusters on-board the vessel. A combination of position reference sensors and environmental sensors give position feedback for control of the position. In particular, DP may be used in oil and gas exploration, where vessels may be extended farther offshore from land in water depth sufficiently great that it is impractical to use anchor mooring systems.
However, the ability of the propeller and/or thrusters to maintain the desired position of the vessel may be limited by various factors. For example, the ability to change direction of a propeller, e.g., to change the thrusting force generated, may be too slow relative to the bandwidth requirements for accurate position control. Along these lines, therefore, the dynamic range of the thrust may be limited at higher bandwidths, especially with regard to the ability to reverse the thrust direction. As such, position control accuracy may degrade under some conditions depending on the particular wind direction, waves, etc.